PREHEAT oven to 350°F. Spray both sides of Tortillas with cooking spray, then place in a single layer on baking sheet. Bake 10 min. or until crisp and lightly browned.
COOK and season meat with Taco Seasoning as directed on package.
SPREAD each tortilla with 1 Tbsp. of the Nacho Cheese Sauce; top with meat mixture and lettuce. Crumble 1 Taco Shell over each tostada; top with tomato, cheese and salsa.